Simplify HTMLFastPathParser::scanEscapedAttributeValue().
Pull request: https://github.com/WebKit/WebKit/pull/12327
Committed 262531@main (a740a0c0803f): <https://commits.webkit.org/262531@main> Reviewed commits have been landed. Closing PR #12327 and removing active labels.
<rdar://problem/107578858>